Chris Cook, president and CEO of investment adviser Beacon Capital Management, said he nearly pulled his clients’ assets out of Vanguard’s telecom exchange-traded fund earlier this year because the firm was facing liquidity issues when trying to trade large blocks of shares. Beacon manages $3 billion in assets, the vast majority in ETFs tracking the 11 S&P 500 sectors.

“It wasn’t a diversified sector, and that’s why we buy ETFs and invest at the sector level,” he

said.